1. Field of the Invention
This invention relates to a water purifying substance having a high ability to fix phosphoric acid and a method for producing the same, and more particularly to a water purifying substance capable of decreasing the phosphoric acid content contained in sludge accumulated on the bottom of a sewer, lake or other body of water.
2. Description of the Prior Art
Recently, the nitrogen and phosphorous content of wastes or scraps is increasing, thus resulting in an environmental problem from the viewpoint that the wastes containing such nutritious matters intended for the land are dumped into a river, lake, marsh or other body of water. In a sense, the environment is nourished by such wastes and scraps fortified with plenty of nutritious salts such as nitrogen and phosphorous, which flow into the sea, river, lake or marsh via the drainage basins. Thus, the wastes are of high nutritive value primarily for plant plankton and are accumulated on the bottom of the body of water.
With this increase in the nourishment of the environmental system, however, harmful plant plankton causing such problems as water-bloom and red tide are bred on a massive scale, thus coloring the water of the lake or other body of water green or brown. The environmental pollution often causes damage to the marine products industry, fish-raising industry and so forth, and causes anxiety about the safety of the water.
There are thought to be two routes by which phosphoric acid serving as a nutrient for microorganisms reaches an environmental system such as a lake and so on. These routes are as follows:
(1) Waste water fortified with phosphoric acid that flows into the lake or the like. PA0 (2) Phosphoric acid held in sludge that accumulates on the lake bottom. PA0 (A) To solve the aforenoted problem (a), there may be adopted a method of absorbing the pollutant in question by use of an adhering biological membrane such as used in a common liquid-waste treatment; an absorbent such as activated charcoal capable of absorbing even small quantities of organic and stinking substances; or a modern reaction device of an ozone-oxidation type which methods are capable of cleaning up city waste water to a high degree. PA0 (B) A method for solving the aforenoted problem (b) has been practiced by scattering sand all over the body of water to confine the sludge.
These routes have been blocked by the following methods.
However, it has so far been difficult to completely cut off the route of phosphoric acid flowing into the lake or marsh and to prevent the wastes from being fortified by the reasons mentioned below.
To be more specific, the former method (A) for solving the first problem (a) by use of various absorbing means is practiced by connecting into the public sewage system all of the pollution sources, including all sources of domestic waste water from domestic drainage and all sources of industrial liquid waste flowing out from even small factories; purifying the waste water by completely removing the phosphoric acid from the waste water; and then discharging the purified waste water into the lake, river or other body of water. This method is disadvantageous in that it entails too much labor, expense and time to be practicable.
Although the aforesaid method may possibly become practical some day in the future, the technique and facilities for purifying waste water will be accompanied great planning and managing difficulties.
According to the latter method (B) for improving the environment, the polluted sludge in the lake or other water body may be completely covered up with sand, but this is by no means a fundamental solution of the problem because the polluted sludge does not cease to exist.
Incidentally, the self-purification of rivers, land, lakes and marshes has been known since early times. For instance, land has a power to organically decompose substances due to the presence of soil microbes and it contains clay particles essentially possessing the prominent ability to absorb phosphorous.
Therefore, it is desirable to make good use of the purifying abilities of nature without exclusively depending on a wastewater treatment system.